Multi-dimensional force sensor for haptic interaction:a review

Haptic interaction plays an important role in the virtual reality technology,which let a person not only view the 3D virtual environment but also realistically touch the virtual environment.As a key part of haptic interaction,force feedback has become an essential function for the haptic interaction.Therefore,multi-dimensional force sensors are widely used in the fields of virtual reality and augmented reality.In this paper,some conventional multi-dimensional force sensors based on different measurement principles,such as resistive,capacitive,piezoelectric,are briefly introduced.Then the mechanical structures of the elastic body of multi-dimensional force sensors are reviewed.It is obvious that the performance of the multi-dimensional force sensor is mainly dependent upon the mechanical structure of elastic body.Furthermore,the calibration process of the force sensor is analyzed,and problems in calibration are discussed.Interdimensional coupling error is one of the main factors affecting the measurement precision of the multi-dimensional force sensors.Therefore,reducing or even eliminating dimensional coupling error becomes a fundamental requirement in the design of multi-dimensional force sensors,and the decoupling state-of-art of the multi-dimensional force sensors are introduced in this paper.At last,the trends and current challenges of multi-dimensional force sensing technology are proposed.

Characterizing the human-robot haptic dyad in robot therapy of stroke survivors

Purpose–The working hypothesis,on which this paper is built,is that it is advantageous to look at protocols of robot rehabilitation in the general context of human-robot interaction in haptic dyads.The purpose of this paper is to propose a new method to detect and evaluate an index of active participation(AC index),underlying the performance of robot-assisted movements.This is important for avoiding the slacking phenomenon that affects robot therapy.Design/methodology/approach–The evaluation of the AC index is based on a novel technique of assistance which does not use constant or elastic forces but trains of small force impulses,with amplitude adapted to the level of impairment and a frequency of 2 Hz,which is suggested by recent results in the field of intermittent motor control.A preliminary feasibility test of the proposed method was carried out during a haptic reaching task in the absence of visual feedback,for a group of five stroke patients and an equal group of healthy subjects.Findings–The AC index appears to be stable and sensitive to training in both populations of subjects.Originality/value–The main original element of this study is the proposal of the new AC index of voluntary control associated with the new method of pulsed haptic interaction.